1. Technical Field
The present application relates generally to an omni-directional speaker system and, in particular, to an omni-directional speaker system with three-dimensional 360.degree. directivity which can be used for general purpose miniaturization applications and satisfy the user demand of home theatre.
2. Description of the Related Art
Production of omni-directional speaker systems began in 1958 and have been primarily marketed for high fidelity (Hi-Fi) applications by several manufacturers. In general, there are two types of omni-directional speaker systems depending on their structures. One type is comprised of a combination of a plurality of directional speakers. Referring to FIGS. 1A through 1D, schematic views illustrate differently configured conventional speaker systems. For instance, FIG. 1A illustrates a hexahedral cabinet 10 having a speaker unit on each face thereof. FIG. 1B illustrates an octahedral cabinet 20 which also has a speaker unit on each face thereof. FIG. 1C illustrates a spherical cabinet 40 having a plurality of speaker units 11 on its upper, lower, left, and right portions. Despite their high quality omni-directional sound source, one disadvantage associated with these speaker systems is that they are large and heavy, and difficult to fabricate.
Referring now to FIG. 2, a conventional diffuser-type speaker system (i.e., which is the second type of omni-directional speaker system) is shown. The diffuser-type speaker system (which is manufactured by Pioneer Co., Japan) shown in FIG. 2 includes a diffuser 54 on its frontal face. A spherical cabinet 50 is supported by a cabinet leg 51. A sound absorbing material 52 is attached to the inner surface of the cabinet 50 and a speaker unit 53 is directed upward in an upper portion of the cabinet 50. Fixing legs 55 are installed on the cabinet 50 to support the diffuser 54. In operation, sound waves emitted from the speaker unit 53 are reflected from the diffuser 54 on the fixing legs 55 and diffused bi-directionally (as indicated by the arrows) so that a listener can hear stereophonic sound. Although this speaker system design allows the cabinet 50 to be miniaturized, there are limitations in realizing 360.degree. omni-directivity and controlling sound quality. Moreover, due to the lack of sensitivity of the treble and intermediate sound to directivity and the use of a reflecting plate, the sound pressure associated with treble and intermediate sound waves is different from the sound pressure associated with bass sound waves, thereby making it difficult to balance the treble and intermediate sound. As a result, in order to obtain omni-directivity with a single speaker having a diffuser on its front face, either an expensive speaker unit is required to increase the sound pressure level of the treble and intermediate sound or a complicated diffuser must be employed.
Another conventional diffuser type omni-directional speaker system (which is also manufactured by Pioneer Co., Japan) is shown in FIG. 3. The speaker system includes a cylindrical cabinet 60 having an upper and lower portion which are sealed. In the lower portion, a woofer 62 is mounted on a speaker baffle 63 over a diffuser 61. The upper portion of the cylindrical cabinet includes three ducts 64 and three tweeters 65.
During operation of the speaker system, bass sound waves emitted from the woofer 62 are diffused bi-directionally through reflection from the diffuser 61 and sideward through the duct 64. Treble sound waves emitted from the tweeters 65 in the upper portion of the cabinet 60 are diffused bi-directionally so that a listener can listen stereophonic sound. One disadvantage to this speaker system is that it requires a plurality of speakers, thereby increasing the size and weight of the cabinet and making it difficult to realize 360.degree. omni-directivity and control sound quality.